In recent years, apparatuses such as digital still cameras, digital movie cameras and cellular phones utilizing a solid state image pickup element have been widely used. With regard to these apparatuses, in order to minimize the size of the apparatus, the demand for increasing the number of pixels of the solid state image pickup elements such as a CCD Sensor and a CMOS sensor, and for minimizing the size of an optical system has been increased. Consequently, as the number of pixels of the solid state image pickup element increase and the optical system is minimized, the size of the pixel in the solid state image pickup element has been minimized and the light amount entering into each pixel has been decreased. As a result, camera shaking easily occurs.
Further, from the viewpoint of portability and convenience of the these image pickup apparatuses, the demand for making the main body of the apparatus thin and/or the demand of that a lens does not come out from the main body when conducting zooming operation have been increased. In response to these demands, a bending optical axis optical system in which a reflecting member is provided has been proposed.
With regard to the problems of camera shaking, as a device for eliminating the caused shaking, proposed has been a device for correcting caused shaking by providing a detection sensor for detecting the shaking and driving the shaking correction member to cancel the shaking.
An angular velocity sensor is used as the shaking correction sensor. For example, there is known an optical system in which shaking correction is conducted by moving a part of lens components in the optical system in the surface perpendicular to the optical axis of the optical system.
Further, there is proposed an optical system in which a variable vertex angle prism is arranged therein to correct shaking by varying the vertex angle of the prism.
There is proposed an optical system in which shaking is corrected by changing the angle of a reflecting member such as a mirror arranged in the optical system.
FIG. 14 illustrates a shaking correction optical unit 1 based on a conventional technology. In FIG. 14, a symbol 2 denotes a first lens group; a symbol 3 denotes a prism placed on a reference position; a symbol 4 denotes a second lens group, a symbol 5 denotes a third lens group; a symbol 6 denotes a fourth lens group; a symbol 7 denotes a low-pass filter; and a symbol 8 denotes an image pickup element. A symbol 12 denotes the optical axis of the first lens group; a symbol 11 denotes the optical axis of the second lens groups 4, the third lens group 5, and the fourth lens group 6; an optical axis 11 and optical axis 12 cross with the reflection surface of the prism 3 at a point A. A symbol 3a denotes a position of a prism, which is driven an angle of “a” from a reference position centering on the point A to correct the shaking. A symbol 13 denotes an extended line of optical axis 11, which is inflected by the prism rotated to the position 3a and an angle formed by the optical axis 12 and an extended line 13 is equal to 2 a being two times of the angle “a”, which is a rotated angle of the prism.
The first lens group 2, the prism 3, the second lens group 4, the third lens group 5, the fourth lens group 6 and the low-pass filter 7 configure the optical unit 1. The second lens group 4 and the third lens group 5 are a variable magnification optical system, and the second lens group 4 and the third lens group 5 moves in the directions indicated by symbols 9 and 10 on the optical axis 11 to smoothly conduct a zooming operation.
In FIG. 14, when the prism 3 stays at the reference position, a light flux travels on the optical axis 12 of the first lens group 2 and the prism 3 at the reference position makes total reflection for the light flux. The reflected light flux is arranged to travel on the optical axis 11. However, when the prism rotates angle by “a” and stays at the position 3a, the light flux 13, which are shifted by angle “2 a” from the optical axis 12 are reflected by the prism 3 positioned at 3a and travel on the optical axis 11.
With regard to the shaking correction methods other than the methods described above, a method for shifting the image pickup element to the direction to cancel the shaking has been proposed.
However, according to the method of moving a part of the optical system, it is necessary to provide space in which the lens moves and space for placing a mechanism for shifting the lens, which is not suitable for minimizing the body of the apparatus. Further, there is a problem that making the apparatus thin cannot be achieved because of the space, even when utilizing an inflecting optical system to make the apparatus thin. Further, according to this method, if the center of the correction lens shifts and coma aberration is generated, there is another problem that focusing performance of the optical system comes down.
According to the method of changing a vertex angle of a prism, it is necessary to arrange the variable vertex angle prism in the optical path of a photographic lens. Accordingly, there is a problem that the optical system cannot be minimized.
According to the method of changing an angle of an reflection member, when conducting shaking correction by changing the angle of the reflection member, as described when explaining the FIG. 14, optical axes in the front and back sides of the reflection member shift and the light flux originally supposed to travel on the optical axis travel off-axis portion, which results in the deterioration of aberration characteristic.
According to the method for shifting the image pickup element, since it is necessary to maximize the image circle of the photographic lens, there is a problem that the size of the photographic lens becomes large.